Reactive flame retardants for flexible polyurethane foams

ABSTRACT

The present invention provides dialkyl phosphorus-containing compounds, namely reactive mono-hydroxyl-functional dialkyl phosphinates, serving as highly efficient reactive flame retardants in flexible polyurethane foams. The invention further provides fire-retarded polyurethane compositions comprising said the reaction product of the mono-hydroxyl-functional dialkyl phosphinates with polyol and isocyanate foam forming components.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional patentapplication Ser. No. 62/536,260, filed Jul. 24, 2017, the entirecontents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The disclosure herein provides for the use of reactive dialkylphosphorus-containing compounds, namely hydroxyl-functional esters ofdialkyl phosphinic acids, which when reacted with polyol and isocyanate,serve as highly efficient reactive flame retardants in flexiblepolyurethane foams. The invention further provides fire-retardedflexible polyurethane foam with said hydroxyl-functional dialkylphosphinates reacted and incorporated into the polymer matrix of aflexible polyurethane foam. The expressions “fire retardants” and “flameretardants” are used herein interchangeably.

BACKGROUND OF THE INVENTION

Brominated or phosphorus-based flame retardants are known to be highlyeffective and, in many cases, are the only options for reducing the firerisk of synthetic materials such as flexible polyurethane foams.However, the growing public and governmental scrutiny of chemicals, andin particular flame retardants, has increased over the years. The goalis towards more sustainable, reactive, polymeric and/or halogen-free newproducts. Scrutiny greatly diminishes if a flame retardant is reactedinto the polymer matrix and cannot be leached-out.

Thus, there is a demand for reactive phosphorus-containing fireretardants for flexible polyurethane possessing such features as highphosphorus content, clear light color and good compatibility withpolyether polyols and polyester polyols employed in the polyurethaneindustry.

SUMMARY OF THE INVENTION

The present invention provides reactive dialkyl phosphorus-containingmono-hydroxyl-functional compounds possessing highly satisfactoryflame-retarding characteristics and having good compatibility with thepolyol components of a flexible polyurethane foam-forming system. Theexpression “a flexible polyurethane foam-forming system” as used hereinshall be understood to comprise a polyol, an isocyanate and a reactivedialkyl phosphorous-containing mono-hydroxyl functional compound asdescribed herein. The mono-hydroxyl-functional dialkyl phosphinatecompounds are fully reactive through their single hydroxyl-functionalgroup, and can be more easily formulated than di- ortri-hydroxyl-functional dialkyl phosphinate compounds. It has beensurprisingly found that despite its lower content ofhydroxyl-functionality, the reactive mono-hydroxyl functional dialkylphosphinate compounds herein can be reacted and incorporated into thepolymer structure of a flexible polyurethane foam, e.g., by reactionwith the isocyanate component of the flexible polyurethane foam-formingsystem, without disrupting the elastic properties of the flexiblepolyurethane foam. This means that the flame retardants of the inventionbecome integrated into the flexible foam substrate, such that they arenot released into the environment and are not likely to penetratethrough cell membranes of living tissue, and therefore do not pose ahealth hazard. The invention further provides the flexible polyurethanefoam-forming system described above, including but not limited to thereactive dialkyl phosphorus-containing mono-hydroxyl-functionalcompounds described herein.

The term “foam” as used herein refers to flexible polyurethane foams.The flexible polyurethane foam described herein, or claimed herein, ascomprising, consisting essentially of, or consisting of the reactedmono-hydroxyl-functional dialkyl phosphinate compounds of the generalformula (I-A) and/or (I-B), with the general formula (I-B) representingthe group of phosphorus-containing diol and/or polyol reaction productsof the partial phosphorylation of polyalcohols, which contain at leastone phosphorus-containing group, are all understood herein to containthe aforementioned formula(e) as reactive materials, i.e., theaforementioned formula(e) are reacted into the flexible polyurethanematerial's structure, in which case the aforementioned formula(e) maynot be present, or would not be present in the same structuralformula(e) as described herein, but would be present in the flexiblepolyurethane material as a reaction product of a diol and/or polyol, anisocyanate and the structural formula(e) described herein.

The term “polyol” as used herein will be understood as also possiblybeing defined as a diol and/or a polyol.

The present invention provides mono-hydroxyl-functional dialkylphosphinate compounds of the general formula (I-A) and (I-B), and agroup of phosphorus-containing diol and/or polyol reaction products ofthe partial phosphorylation of polyalcohols, which contains at least onephosphorus-containing group of the general formula (1-B), whereinformula (1-A) is:

wherein:

R¹ and R², are selected from a linear or branched alkyl group containingfrom 1 to 4 carbon atoms, such as methyl, ethyl, propyl, isopropyl,butyl, and isobutyl, preferably methyl or ethyl, more preferably both R¹and R² being ethyl; and,

X is either —(Z)_(k)—R³ or

and when X is —(Z)_(k)—R³, Z is —(Y—O)_(n)—, wherein Y is a linear orbranched alkylene group containing from 2 to 8 carbon atoms, preferablyfrom 2 to 4 carbon atoms, more preferably ethylene, propylene, orisopropylene, and n represents an integer from 1 to 20, preferably from1 to 5, and even more preferably from 1 to 2,

k may be 0 or 1;

R³ is selected from hydrogen, a mono-hydroxy-terminated linear orbranched alkylene group containing from 2 to about 8 carbon atoms,preferably from 2 to 4 carbon atoms; and,

provided that when k is zero, R³ is the mono-hydroxy-terminated linearor branched alkylene group and when k is 1, R³ is hydrogen_(—) and

when X is

R⁴ and R⁵ are each independently selected from 1-I, a linear or branchedalkyl group containing from 1 to 8 carbon atoms, preferably from 1 toabout 4 carbon atoms, and most preferably any one of methyl, ethyl orpropyl, a linear or branched alkenyl group containing from 2 to 8 carbonatoms, preferably from 2 to about 4 carbon atoms, a halo-substitutedalkyl group containing from 1 to 8 carbon atoms, an alkoxy groupcontaining from 1 to 8 carbon atoms, preferably from 1 to about 4 carbonatoms, an aryl group containing from 6 to 12 carbon atoms, preferablyfrom 6 to about 8 carbon atoms, and an alkylaryl group containing from 7to 16 carbon atoms, preferably from 7 to about 12 carbon atoms, or R⁴and R⁵ are bonded to each other to form a cycloalkyl group containingfrom 4 to about 8 carbon atoms, preferably 6 carbon atoms; and whereinformula (I-B) is:

wherein:

R¹ and R², are independently selected from a linear or branched alkylgroup containing from 1 to 4 carbon atoms, such as from methyl, ethyl,propyl, isopropyl, butyl, and isobutyl, preferably methyl or ethyl, morepreferably both R¹ and R² both being ethyl; and,

n¹ is an integer equal to or greater than 1, and n² is one, preferablyn¹ is from about 1 to about 5 and.

Z² is a moiety derived from a diol or polyol which has a valence ofn¹+n², and is of the general formula:

wherein R is selected from the group consisting of:

and where each R⁶ independently is H or is an alkyl of from 1 to 4carbon atoms, x is 0 or ≥1, preferably 1 to 4, more preferably x=1, y is2 or 3; z is an integer of from 2 to 5; and, m>1, preferably m=1.

There is also provided herein a process for the preparation of thesecompounds.

The novel compounds of formula (1-A) can be prepared by the reaction ofmono-hydroxyl-functional-dialkyl phosphinic acids of formula (II) withcompounds having an oxirane group, wherein formula (II) is:

wherein R¹ and R² are as defined.

The compounds of formula (I-A) can also be prepared by the reaction ofdialkyl phosphinic halides of formula (III) with aliphatic diols,wherein formula. (III) is:

and wherein R¹ and R², are as defined, and A is chlorine or bromine.

The phosphorus-containing diols and/or polyols of the invention, forexample those of formula I-B, can be prepared by the reaction of dialkylphosphinic halides of formula (III) with aliphatic diols and/or polyols.

The reactive mono-hydroxyl-functional dialkyl phosphinates of thisinvention possess high phosphorus content, have good hydrolytic andthermal stability, exhibit good compatibility with the diol and/orpolyol components of the flexible polyurethane foam-forming system, andare useful as highly efficient reactive flame retardants in flexiblepolyurethane foams.

The present invention further provides fire-retarded flexiblepolyurethane comprising the reactive residue of saidphosphorus-containing mono-hydroxyl-functional compounds after beingreacted in the flexible polyurethane foam-forming system to form theflexible polyurethane foam. The phosphorus-containingmono-hydroxyl-functional compounds herein can be used in the flexiblepolyurethane foam-forming system either individually or in an admixturewith one another, and/or with other flame retardants, includinghalogen-containing flame retardants and phosphorus-containing flameretardants.

All the above and other characteristics and advantages of the inventionwill be better understood through the following illustrative andnon-limitative detailed description of the preferred embodimentsthereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In one embodiment the mono-hydroxyl-functional dialkyl phosphinates offormula (I-A) can be those of the more specific formulae (I-A-1) or(I-A-2), wherein formula (I-A-1) is:

wherein R¹ and R², Z, k, and R³ are as defined above; and,

-   wherein formula (I-A-2) is:

and wherein R¹, R², R⁴ and R⁵ are as defined above.

In one embodiment herein, the mono-hydroxyl-functional dialkylphosphinates of formula (I-A) of the present invention are prepared bythe reaction of dialkyl phosphinic acids of formula (II) with compoundsof formula (IV), having oxirane groups, which formula (IV) is

wherein:

-   R⁴ and R⁵ are as defined above.

In one other embodiment herein, the mono-hydroxyl-functional dialkylphosphinates of formula (I-A) of the present invention are prepared bythe reaction of dialkyl phosphinic halides of formula (III) withaliphatic diols of formula (V):

HO—(Z)_(k)—R³   (V)

wherein Z, R³ and the subscript k are as defined above.

The phosphorus-containing diols and/or polyols of the present invention,for example those of formula (I-B), are prepared by the reaction ofdialkyl phosphinic halides of formula (III) with aliphatic diols orpolyols.

The dialkyl phosphinic acids (II) and dialkyl phosphinic halides (III)employed as starting materials in the process of the present inventionare for the most pail well known in the art. The compounds of formula(II) can be obtained for example by hydrolysis of the correspondingdialkyl phosphinic halides ([10. The latter can be prepared for exampleby the method described in U.S. Pat. No. 3,104,259, the entire contentsof which are incorporated by reference herein.

Specific oxirane compounds used in the process for preparing thecompounds of formula (I-A) or more specifically (I-A-1) or (I-A-2) ofthe present invention are selected from the group consisting of, but notlimited to, for example, ethylene oxide, propylene oxide,1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxy-5-hexene,1,2-epoxy-2-methylpropane, 1,2-epoxyoctane, glycidyl methyl ether,glycidyl isopropyl ether, glycidyl isobutyl ether, glycidyl heptylether, glycidyl 2-ethylhexyl ether, glycidyl allyl ether,trimethylolpropane tri glycidyl ether, styrene oxide, cyclohexene oxide,epichlorohydrin and combinations thereof. More preferably, ethyleneoxide, propylene oxide and 1,2-epoxybutane are used as the oxiranecompound.

Specific aliphatic diols used in the process for preparing the compoundsof formula (I-A) or more specifically (I-A-1) or (I-A-2) of the presentinvention are selected from the group consisting of, but not limited to,for example, ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propanediol, 1,4-butane diol, 2-butene-1,4-diol, 1,5-pentane diol, 1,6-hexanediol, 1,8-octane diol, and other diols having molecular weights up to700.

The aliphatic diols and/or polyols used in the process for preparing thephosphorus-containing polyols of the invention can generally be anysuitable diols and/or polyols having at least two or at least threereactive hydrogen atoms, respectively, examples being those havingfunctionality of from 2 or 3 to 6, preferably, 2, 3 and 4, andpreferably a molecular weight of from about 100 to about 700. Specificaliphatic diols and/or polyols can be selected from the group ofnon-polymeric polyalcohols, for example, trimethylol propane,trimethylol ethane or glycerol.

Preferably, the diols and/or polyols to be used according to the presentinvention are polyether diols and/or polyols. This class of diols and/orpolyols is obtained by the ring-opening addition reaction of one or morealkylene oxides (e.g., ethylene oxide and propylene oxide) with asuitable reactant containing one or more active hydrogen atoms, such asalcohols, amine and acids; more specifically, said reactant may beselected from a group consisting of diols, triols, novolac resins,pentaerythritol, sorbitol, sucrose, diethylenetriamine and the like.Polyester-polyols may also be used according to the present invention;this class of polyols is obtained by the condensation reaction ofcarboxylic, dicarboxylic (or polycarboxylic) acid, such as adipic acid,phthalic acid or the like, with diols or triols. The aliphatic diolsand/or polyols used in the process for preparing thephosphorus-containing mono-ols, diols or polyols of the presentinvention are selected from polymeric diols and/or polyols such aspolyether polyols, polyester polyols, and mixtures thereof.

In a preferred embodiment of the present invention, the reaction ofdialkyl phosphinic acids (II) with an oxirane compound is carried out ina medium of excess oxirane, with or without an organic solvent such astetrahydrofuran, 1,4-dioxane, or toluene.

The amount of oxirane compound used in the reaction with mono-hydroxydialkyl phosphinic acids (11) is a 5-300% molar excess relative to themono-hydroxy dialkyl phosphinic acid, and preferably a 50-100% molarexcess. Using a molar excess of the oxirane compound greater than 100%relative to the mono-hydroxy dialkyl phosphinic acid is inexpedient dueto the need to recycle a large quantity of oxirane.

The mono-hydroxyl-functional dialkyl phosphinates of formula (I-A) ormore specifically (1-A-1) or (1-A-2) of the present invention have aphosphorus content of about 8-18% by weight and a hydroxyl number ofabout 150-315 mg KOH/g, depending on the dialkyl phosphinic acid and theoxirane taken for the reaction.

It is preferred, for the preparation of the targetmono-hydroxyl-functional dialkyl phosphinates (I-A) or more specifically(I-A-1) or (I-A-2) with the highest possible phosphorus content, toreact mono-hydroxy-dialkyl phosphinic acids having the highestphosphorus content amongst the mono-hydroxy dialkyl phosphinic acids(II), with ethylene oxide and propylene oxide.

Thus, the compounds of formula (I-A) or more specifically (I-A-1) orhaving particularly valuable properties are those wherein R¹, and R² areeach ethyl.

Said reactions are carried out at a temperature of between 40° C. and120° C., and preferably between 70° C. and 90° C. At a temperature lowerthan 40° C. the reaction becomes unacceptably slow. On the other hand,applying a temperature higher than 120° C. is not advisable since atsuch temperatures undesirable decomposition products may he formed.

In a preferred embodiment, the reaction of dialkyl phosphinic halides(III) with an aliphatic diol is carried out in a medium of excess diol.

The amount of diol compound used in the reaction with dialkyl phosphinichalides (III) is generally 2 to 10 moles per 1 mole dialkyl phosphinichalide, and preferably a 4 to 8 moles molar excess. The relatively largeexcessive amounts of these diols are required for minimizing theformation of undesirable bis(dialkyl phosphinate) esters of glycols anddiols having no hydroxyl groups. Using a molar excess of the diolcompound greater than 10 moles per 1 mole dialkyl phosphinic halide isinexpedient due to the need to recycle a large quantity of diol.

The mono-hydroxyl-functional dialkyl phosphinates of formula (I-A) ormore specifically (I-A-1) or (I-A-2) of the present invention have aphosphorus content of about 2-18% by weight and a hydroxyl number ofabout 150-450 mg KOH/g, depending on the &alkyl phosphinic halide andthe diol taken for the reaction.

It is preferred, for the preparation of the targetmono-hydroxyl-functional dialkyl phosphinates (I-A) or more specifically(I-A-1) or (I-A-2) with the highest possible phosphorus content, toreact dialkyl phosphinic halides having the highest phosphorus contentamongst ⁻the dialkyl phosphinic halides (111), with ethylene glycol.

Thus, the compound of formula (I-A-1) having particularly valuableproperties, is that wherein R¹ and R² are each ethyl, k is 1, n is 1. Yis —CH₂CH₂—, and R¹ is hydrogen.

Said reactions are carried out at a temperature of between 25° C. and120° C., and preferably between 50° C. and 90° C. Applying a temperaturelower than 25° C. results in a low yield. On the other hand, applying atemperature higher than 120° C. is not advisable since at suchtemperatures undesirable decomposition products may be formed. Inaddition, a catalyst can be used to accelerate reaction for exampleMgCl₂ or ZnCl₂.

In a preferred embodiment the reaction of dialkyl phosphinic halides(III) with an aliphatic diol is carried out in the presence of a strongbase such as sodium hydroxide or potassium hydroxide, in a medium ofboth an organic solvent and an excess aliphatic alcohol. The organicsolvent is selected from aromatic compounds. Especially suitablearomatic solvents are chlorobenzene, ortho-dichlorobenzene, mesitylene,and in particular, toluene and xylene. An effective amount of the baseemployed in the process is in a range of 1-1.2 mol per 1 mol dialkylphosphinic halides (III), and preferably 1-1.05 mol.

Sodium or potassium hydroxide can be employed in a solid form. Waterresulting from the reaction between the diol and the base should beeliminated from the reaction mixture as much as possible prior to theaddition of dialkyl phosphinic halides (III).

In a preferred embodiment, the reaction of dialkyl phosphinic halides(III) with an aliphatic diol and/or polyol is carried out by varying thedegree of partial phosphorylation of the diol and/or polyol. Thephosphorus-containing diol and/or polyol according to the presentinvention comprises at least one phosphorus-containing group. Thisphosphorus-containing group is a group of formula (III-A).

wherein:

wherein R¹ and R² are as defined, and wherein the wavy line indicates abond to a diol or polyol via an oxygen atom.

The phosphorus-containing diol and/or polyol of the invention can alsocomprise two or more phosphorus-containing groups of formula (III-A),wherein these phosphorus-containing groups can be identical ordifferent.

The reaction of dialkyl phosphinic halides (III) with an aliphatic dioland/or polyol can be carried out in the presence of an organic basewhich is selected from, but not limited to, the group of tertiaryamines, for example, triethylamine, pyridine, diisopropyl ethyl amine,1-methylimidazole. The amount of base used is equimolar to dialkylphosphinic halide (IlI). The base can also he used in excess to thedialkyl phosphinic halide. Said reactions are typically carried out in amedium of inert organic solvent. Suitable solvents for thephosphorylation are, but not limited to, halogenated hydrocarbons, suchas methylene chloride, chloroform or 1,2-dichloroethane. Solvents whichare further suitable are ethers such as dioxane or tetrahydrofuran.Solvents which are further suitable are hydrocarbons such as hexane ortoluene.

In a preferred embodiment the reaction of dialkyl phosphinic halides(III) with an aliphatic diol and/or polyol is carried out in thepresence of a strong inorganic base such as sodium hydroxide orpotassium hydroxide, in a medium of an organic solvent such aschlorobenzene, mesitylene, and in particular, toluene and xylene.

An effective amount of the base employed in the process is in a range of1-1.2 mol per 1 mol dialkyl phosphinic halides OM, and preferably 1-1.05mol. Sodium or potassium hydroxide can be employed in a solid form.Water resulting from the reaction between the diol, and/or polyol andthe base should be eliminated from the reaction mixture as much aspossible prior to the addition of dialkyl phosphinic halides (III).

The amounts of dialkyl phosphinic halide (III) and diol and/or polyolcan be adjusted so that the desired degree of functionalization isattained. Partial phosphorylation of the diol and/or polyol can beachieved by using less than the stoichiometric amount of the dialkylphosphinic halide (III) to the diol and/or polyol based on itsfunctionality. In this way, only a portion of the OH groups in the dioland/or polyol is reacted with dialkyl phosphinic halide.

The phosphorus-containing diol and/or polyol of the present invention(also described herein as the partially phosphorylated diol and/orpolyol) has a remaining average OH-functionality (followingphosphorylation thereof) of 1 and a molecular weight of from about 200to about 1000. The phosphorus-containing diols and/or polyols of thepresent invention have a phosphorus content of about 4-20% by weight anda hydroxyl number of about 20-800 mg KOH/g, depending on the dialkylphosphinic halide and the diol and/or polyol taken for the reaction, andon the molar ratio between them.

The diol and/or polyol phosphorylation reactions are carried out at atemperature of between 0° C. and 100° C., and preferably between 10° C.and 90° C. Applying a temperature lower than 0° C. results in a lowreaction rate. On the other hand, applying a temperature higher than100° C. is not advisable since at such temperatures undesirabledecomposition products may be formed.

The following examples illustrate specific embodiments of both thepreparation of certain compounds of the invention and the utility ofthese compounds as reactive flame retardants in flexible polyurethanefoams.

The compounds of the invention are useful as reactive flame retardants.The flame retardants may be used as-is, or as a mixture with halogenatedor non-halogenated products. For flexible polyurethane foams it ispreferred to use halogen-free hydroxyl-functional dialkyl phosphinatesof the invention either pure or with other non-halogenated products.

The compounds of the present invention are highly efficient reactiveflame retardants when incorporated into flexible polyurethane foams. Itshould be noted that the compounds of the invention are useful over abroad Isocyanate Index (abbreviated herein MDI or TDI). The index refersto the ratio of isocyanate practically used in the formulation vs. thetheoretical stoichiometric amount of isocyanate required, expressed inpercentages.

The flexible polyurethane foams herein contain a typicalflame-retardant-effective amount of the composition of this invention.Typically, the compositions of this invention are applied in amountsthat provide a total phosphorus concentration in the polymer (i.e., theflexible polyurethane foam) in the range of 0.3 to 15 wt %, based on thetotal weight of the polymer. Preferably, the total phosphorusconcentration in the polymer is in the range of I to 10 wt % and morepreferably, in the range of 1.5 to 5 wt %, based on the total weight ofthe flexible polyurethane polymer. Most preferably, the amounts used ofthe reactive flame retardants of this invention are at least sufficientto meet the current requirements of the flammability Test Method MUSS302.

By suitable choice of components and conditions, the flexiblepolyurethane foams are made which may vary in properties as to thedegree of flexibility. Thus, flexible foams are generally made frompolymeric diols or triols having hydroxyl numbers of from 20 to 80 usingwater as the principal foaming agent.

The flexible polyurethane foams of the present invention can contain theappropriate choice of auxiliary agents, for example catalysts,surfactants, foam stabilizers and the like.

Flexible polyurethane foams as used herein is made using a diol and/orpolyol having a 3,000 to about 6,000 molecular weight diol and/or polyolas described herein, e.g., a. polyether triol prepared by the additionof propylene oxide to glycerol. A flexible polyurethane foam as usedherein is characterized by having a core impact resilience of at most30% and a glass transition point of from −80° C. to −60° C. Here, theflexible polyurethane foam preferably has a hard segment content of atmost 40 mass %. Conventional flexible polyurethane foam having a bulkfoam density of 2.5 pounds per cubic foot (PCF) or lower and having afoam hardness or (measured in accordance with test method. ASTM3574-Test B1) in a range of 10 to 90 lb/50 in².

The method of making the flexible polyurethane foam of the invention cancomprise combining the diol and/or polyol component and/or theisocyanate component or catalyst and one or more of the flame retardantmaterials of Formulae (I-A), (I-A-1), (I-A-2) and (I-B) described hereinwhich may be metered and pumped into a common mixing vessel, and thenthe resulting mixture may easily be moved to the polymerization site foruse in molds, slab stock operations, etc.

The reactive flame retardants of the invention herein may also beadmixed with the diol and/or polyol reactant before combination with theisocyanate reactant. It is also within the scope of the invention to mixthe reactive flame retardant materials with the isocyanate beforecombining such mixture with the diol and/or polyol reactant. However, ifthe isocyanate and the aforementioned flame retardant materials aremixed and allowed to stand at room temperature for a substantial periodof time, reaction may occur. The “reaction product” as used in theclaims and specification herein, can in one embodiment comprise reactingthe contents of the flexible polyurethane foam-forming system in any oneof the aforementioned methods, and may further include reacting thereactive flame retardant via a pre-polymer technique, such as forexample, reacting an excess of isocyanate with polyol to form anisocyanate terminated pre-polymer and then further reacting theprepolymer with the reactive flame retardant herein.

The flame retardant materials of Formulae (I-A), (I-A-1), (I-A-2) and(I-B) described herein may be described as isocyanate-reactive(NCO-reactive) materials, i.e., they are reactive with the isocyanatesthrough the hydroxyl group(s).

The diols and/or polyols used in making the flexible polyurethane foamsdescribed herein can include any organic polyol, including diols,polyols, and poly:ether, polyester, polyesteramide polyols havinghydrogen atoms that are reactive with isocyanates may be used.Generally, these materials have molecular weights ranging from about 62to about 5,000 and have from 2 to about 10 or more hydroxyl groups permolecule and weight percent hydroxyl contents ranging from about 0.5 toabout 25%. The generally have hydroxyl numbers of from about 50 to ashigh as 500 or even 700.

In the polyester-polyol type of reactant the acid number should be lessthan 10 is usually as close to 0 as possible. These materials arereferred to conveniently as the “polyol'” reactant. The useful activehydrogen-containing diol and/or polyols include the large family ofadduct compounds which result when ethylene oxide, propylene oxide, 1,2-and 2,3-butylene oxide, or other alkylene oxides are added to suchactive hydrogen compounds such as diols, glycols and polyols presentedby ethylene glycol, propylene glycol, glycerine, methyl glucoside,sucrose, sorbitol, hexanetriol trimethylol propane, pentaerythritol aswell as various alkylamines and alkylenediamines, andpolyalkylenepolyamines and the like. Various amounts of these alkyleneoxides may be added to the base diol, polyol or amine molecules referredto, depending upon the intended use of the polyurethane.

For example, a diol and/or polyol for use in making flexible foams couldbe well represented by glycerine to which sufficient propylene oxide wasadded to give a final hydroxyl content of about 1.7%. Such a materialwould have a molecular weight of about 3,000 and have a molar ratio ofglycerine to propylene oxide of about 1 glycerine to 50 propylene oxide.

This technique of controlling flexibility by selection of the dioland/or polyol molecule and the subsequent amount of alkylene oxide addedis well known to those in the art.

In addition to the glycols and the like which can serve as the basepolyol molecule for addition of the alkylene oxides and thus yield the“polyol” molecule for reaction with the isocyanate, one can use astarting molecule which contains primary and/or secondary amine groupswhich have hydrogen reactive toward alkylene oxides. Here also, thequantity of alkylene oxide added depends on the intended uses of thefinal polyurethane products. In the flexible polyurethane productsherein alkylene oxide would be used to produce polyols with lowerhydroxyl content, such as from about 0.1% to about 5% or 10%.

Representative amines which may serve as active-hydrogen containingmolecules for reaction with epoxides are those having from 1 to about 6or more amino nitrogens, examples of which are ethyl amine, ethylenediamine, diethylenetriamine, triethylenetetramine,tetrapropylenepentamine and other linear saturated aliphatic alkyleneamines, the important requirement being at least two, and preferablymore, say 3 to 8 or 10 active hydrogen sites to which the alkylene oxidemay be added.

It is also well known to use the hydroxyl bearing molecules which havebeen prepared by esterification type reactions from polyfunctional acidsor anhydrides and polyfunctional alcohols as the active hydrogencompounds used in preparing the polyurethane systems. These compoundsare often called polyester polyols. Typical acids used in making thesepolyester polyols are maleic, phthalic, succinic, fumaric,tetrahydrophthalic, chlorendic, and tetrachlorophthalic acids. Typicaldiols and/or polyols are ethylene, propylene, butylene, diethylene, anddipropylene, glycols, and polyethylene, polypropylene, glycols andglycerine, trimethylol propane, hexanetriol, pentaerythritol, sorbitoland the like. Where available the above mentioned acids may be used inthe anhydride form if desired.

In making the polyester-polyols, any of the various polyfunctional acidsor anhydrides or mixtures thereof are caused to react with any of thediols, glycols or polyols or mixtures thereof, using a stoichiometricexcess of the hydroxyl groups such that the final polyol productcontains predominantly hydroxyl end groups. The degree of hydroxylfunctionality and the percent hydroxyl is easily varied to provide thedesired polyols by technology and techniques which are known to thoseskilled in the art.

In the art and technology of making flexible polyurethanes, it is alsoknown to employ what is called prepolymer techniques. This is atechnique wherein part of the reaction involved in making flexiblepolyurethane is carried out yielding a prepolymer of increased molecularweight and with either resultant end groups of hydroxyls or isocyanatesdepending on the stoichiometric used in making this prepolymer. Thisprepolymer is then used to prepare the final flexible polyurethaneproduct by reacting it with either a isocyanate or polyol, depending on,as mentioned above, whether the terminal groups of the prepolymer arehydroxyls or isocyanates, respectively.

Broadly, any of the prior art polyesters, isocyanate-modified-polyesterprepolymers, polyesteramides, isocyanate-modified-polyesteramides,alkylene glycols, isocyanate-modified alkylene glycols, polyoxyalkyleneglycols, isocyanate-modified polyoxyalkylene glycols, etc., having freereactive hydrogens and especially hydroxyl groups may be employed forthe production of the polyurethanes described herein.

Examples of isocyanates which can be used include those having two ormore isocyanate groups which have heretofore been used for makingflexible polyurethane foams. Examples of such isocyanate compoundsinclude aromatic isocyanates, aliphatic isocyanates and alicyclicisocyanates, as well as mixtures of two or more of such isocyanates, andmodified isocyanates obtained by the modification of such isocyanates.Specific examples of such isocyanates are toluene diisocyanate,diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate(crude MDI), xylylene diisocyanate, isophorone diisocyanate andhexamethylene diisocyanate; and modified products of such isocyanates,such as carbodiimide-modified products, biuret-modified products, dimersand trimers. Prepolymers with terminal isocyanate groups obtained fromsuch isocyanates and active hydrogen-containing compounds can also beused.

In one embodiment, the isocyanate index range for flexible polyurethanefoams can be from about 130 to about 80, more preferably, from about 120to about 90 and most preferably from about 115 to about 95.

As the blowing agent in the flexible polyurethane foam-formingcomposition of the present invention, known blowing agents heretoforeused in such compositions are suitably selected according to theproperties required of the foamed product.

In the present invention, a cross-linking agent is also used as the caserequires.

As the cross-linking agent, a compound having at least two functionalgroups having active hydrogen, such as hydroxyl groups, primary aminogroups or secondary amino groups is preferred. However, in a case wherea polyol compound is used as the cross-linking agent, the following istaken into account. Namely, a polyol compound having a hydroxyl value ofat least 50 mg KOH/g and more than four functional groups, is consideredto be the cross-linking agent, and a polyol which does not satisfy this,is considered to be any one of polyols of the above-mentioned polyolmixture (polyol (1), (2) or other polyol). Further, two or morecross-linking agents may be used together. As specific examples, apolyhydric alcohol such as dextrose, sorbitol or sucrose; a polyolhaving an alkylene oxide added to a polyhydric alcohol; an aminecompound such as monoethanolamine, diethanolamine, ethylenediamine,3,5-diethyl-2,4 (or 2,6)-diaminotoluene (DETDA),2-chloro-p-phenylenediamine (CPA), 3,5-bis(methylthio)-2,4 (or2,6)-diaminotoluene, 1-trifluoromethyl-4-chloro-3,5-diaminobenzene,2,4-toluenediamine, 2,6-toluenediamine,bis(3,5-dimethyl-4-aminophenyl)methane, 4,4′-diaminodiphenylmethane,m-xylylenediamine, 1,4-diaminohexane, 1,3-bis(aminomethyl)cyclohexane orisophoronediamine; and a compound obtained by adding an alkylene oxidethereto, may, for example, be mentioned.

When the above cross-linking agent is used, even in a case where, forexample, a large amount of a blowing agent is used to produce a flexiblefoam having a low density, the foaming stability will be good, and itwill be possible to produce such a flexible foam. Especially when a dioland/or polyol having a high-molecular weight is used, it is possible toproduce a flexible foam having a low density which used to be considereddifficult to foam. Further, when the cross-linking agent is used, thedurability will be improved, as compared with a case where it is notused. In a case where a diol and/or polyol having a high-molecularweight is used as in the present invention, the foaming stability canreadily be improved particularly when a compound having a relativelyhigh-molecular weight, such as a molec a weight of at least 4000, isused.

Water is a typical example of such a blowing agent; other examplesinclude methylene chloride, n-butane, isobutane, n-pentane, iso-pentane,dimethyl ether, acetone, carbon dioxide, and the like. Depending on thedesired density and other properties of the foamed polyurethane, theseand other blowing agents can be used alone or in combinations of two ormore in a manner known in the art.

The amount of blowing agent to be used is not particularly limited butwill ordinarily range from 0.1 to 20 parts by weight per 100 parts byweight of the diol and/or polyol component of the foam-formingcomposition. Preferably, the amount of blowing agent(s) will be such asto provide a foam density of from 0.8 to 2.5 pounds per cubic foot, andpreferably from 0.9 to 2.0 pounds per cubic foot.

The polyurethane foam-forming composition herein can preferably containany of the catalysts, and combination of catalysts, heretofore known orused for the production of polyurethane foams. Examples of usefulcatalysts include sodium hydroxide, sodium acetate, tertiary amines ormaterials which generate tertiary amines such as trimethylamine,triethylene diamine, N-methyl morpholine, N,N-dimethyl cyclohexylamine,and N,N-dimethyl aminoethanol. Also applicable are metal compounds suchas hydrocarbon tin alkyl carboxylates, dibutyl tin diacetate, dibutyltin dioctoate dibutyl tin dilaurate and stannous octoate; as well asother compounds intended to promote trimerization of the isocyanate suchas, 2,4,6-tris(N,N-dimethylamino-methyl)phenol,1,3,5-tris(N,N-dimethyl-3-aminopropyl)-S-hexahydrotriazine, potassiumoctoate, potassium acetate and catalysts such as DABCO TMR® and POLYCAT43®.

Many other kinds of catalysts can be substituted for those listed above,if desired. The amount of catalyst used can advantageously range from0.05 to 5 weight percent or more based on the total weight of dioland/or polyol in the foam-forming mixture.

The isocyanate (NCO) index which is applied in making the flexible foamaccording to the present invention is 95-125 and preferably 100-120. Itis commonly understood that the NCO index of polyurethane foams is fromabout 80-130.

The densities of the flexible polyurethane foams herein may range offrom 14-80 and preferably 16-55 and most preferably 20-40 kg/m³.

Surfactants, including organic surfactants and silicone-basedsurfactants, may be added to serve as cell stabilizers. Somerepresentative materials are sold under the designations SF-1109, L-520,L-521 and DC-193, Which are, generally, polysiloxane polyoxylalkyleneblock copolymers. Also included are organic surfactants containingpolyoxy-ethylene-polyoxybutylene block copolymers. It is particularlydesirable to employ a minor amount of a surfactant to stabilize thefoaming reaction mixture until it cures. Other surfactants that may beuseful herein are polyethylene glycol ethers of long-chain alcohols,tertiary amine or alkanolamine salts of long-chain allyl acid sulfateesters, alkylsulfonic esters, alkyl aryisulfonic acids, and combinationsthereof. Such surfactants are employed in amounts sufficient tostabilize the foaming reaction against collapse and the formation oflarge uneven cells. Typically, a surfactant total amount from about 0.2to about 3 wt %, based on the formulation as a whole, is sufficient forthis purpose. However, it may be in some embodiments desirable toinclude some surfactants, e.g., DABCO DC-5598, available from AirProducts and Chemicals, Inc., in a higher amount. In view of this asurfactant may be included in the inventive formulations in any amountranging from 0 to 6 wt. %, based on the diol and/or polyol component.

Finally, other additives such as fillers and pigments may be included inthe polyurethane foam-forming formulations described herein. Such mayinclude, in non-limiting embodiments, barium sulfate, calcium carbonate,graphite, carbon black, titanium dioxide, iron oxide, microspheres,alumina trihydrate, wollastonite, prepared glass fibers (dropped orcontinuous), polyester fibers, other polymeric fibers, combinationsthereof, and the like. Those skilled in the art will be aware withoutfurther instruction as to typical and suitable means and methods toadapt the inventive formulations to produce flexible polyurethane foamsthat, though still falling within the scope of the claims appendedhereto, exhibit or benefit from desired property and/or processingmodifications.

The flexible polyurethane foams described herein, be they be can beutilized in the construction and formation of various articles such asfurniture, bedding, and automotive seat cushions, more specifically,furniture applications, automotive applications, boating applications,bus seating applications, train seating applications, RV seatingapplications, office furniture seating applications, aviationapplications, tractor applications, bicycle applications, engine mountapplications, compressor applications, bedding applications, insulationapplications, sporting goods applications, shoe applications, carpetcushioning applications, packaging applications, textile applications,buffer cushioning applications, HVAC applications, tent applications,life raft applications, luggage applications, and hand bag applications.

Flexible siabstock polyurethane foam can be used for furniture, e.g.,upholstered furniture, such as cushions, backs and arms, the automotiveindustry, such as seat and back cushions, and head linings and headrests, for automobiles and trucks, for public transport seating, such asbusses and airplanes, as well as in any of tractor, bicycle andmotorcycle seats including, but not limited to vehicle seat bottom andback bolsters, and armrests, as well as support rings for run flattires, and other automobile interior components; bedding such asmattresses, as sound insulation materials, automobile interiorcomponents such as an arm rest, a steering wheel and a shift lever knob,shoe soles, and sporting goods.

EXAMPLES Preparation Example

A 2-liter, jacketed, hastelloy reactor equipped with a mechanicalstiffer, oil heater and positive displacement laboratory pump wascharged with diethyl phosphinic acid (779 g, 6.38 mol) and sealed. Thereactor was heated to an internal temperature of 45° C. Propylene oxide(743 g, 12.77 mol) was added to the reactor via the pump over two hourswith the temperature being maintained below 65° C. Subsequently thereactor internal temperature was increased to 90° C. and maintainedthere for three hours. The excess propylene oxide was evaporated and theresidue was distilled under vacuum (300-500 mTorr) using a wiped filmevaporator at a jacket temperature of 125° C. The target fraction wascollected as a clear, colorless liquid. The yield was 90% with respectto the starting diethyl phosphinic acid. The product was a mixture oftwo isomers of hydroxyl-functional esters of diethyl phosphinic acid,³¹P NMR (acetic acid-d₄, ppm): 66.8-67.7; and had an acid# of 0.4 mgKOH/g and a phosphorus content of 15.9%.

Preparation Example 2

A 1-liter flask, with a heating mantle, mechanical stirrer, refluxcondenser, dip tube, j-chem controller and thermocouple, and causticscrubber was charged with diethyl phosphinic acid (469 g, 3.84 mol). Theflask was heated to 80° C. and ethylene oxide from a pressurizedcylinder was charged into the reactor through the dip tube over fivehours. Final molar ratio of ethylene oxide to diethyl phosphinic acidwas 1.33. The reaction mixture was kept at 80° C. for additional threehours. Further nitrogen was passed through the dip tube to remove theexcess ethylene oxide. A batch distillation of the residue was done at150° C. and 200 mTorr resulting in a clear liquid (400 g). The productwas 2-hydroxyethyl ester of diethyl phosphinic acid, ³¹P NMR (CDCl₃,ppm) 79; and had an acid# of 0.4 mg KOH/g.

Application of the new compounds of the present invention isdemonstrated through their use as flame retardants in standardformulations for flexible polyurethane foams (Application Example 3).

In addition to the new flame retardant compounds, the followingcomponents were used in preparation of the polyurethane foams:

Materials Manufacturer Voranol 8136 Polyether Polyol Dow Desmophen60WB01 Polyester Polyol Covestro Niax A-1 amine catalyst Momentive NiaxC-131 NPF Momentive Niax DMP Momentive Niax L-537XF Momentive Niax L-620Momentive Dabco 33 LV amine catalyst Air Products T-9 Stannous octoatecatalyst Air products TDI 80 Everchem Specialty Chemicals TDI 65Everchem Specialty Chemicals New FR Product (from Example 1) ICL FyrolFR-2, Fyrol A300-TB ICL

Application Example 3

Foam samples were prepared by mixing the polyol and the New FR Productfrom Preparation Example 1, The remaining components of the formulation,including water, amine catalyst, silicone surfactant and tin catalyst(except for the isocyanate), were added and stirred into the polyol/FRProduct mixture at 2000 rpm for 30 seconds for polyether foam, and 1000rpm for 60 seconds for polyester foam. Immediately after addition andincorporation of the isocyanate into the reaction mixture with vigorousstirring, the complete reaction mixture was then poured into an 8×8×5″(20×20×20 cm) box and allowed to rise fully. For polyether foam, the boxwas then placed in a ventilated hood for 24 hours curing at roomtemperature; for polyester foam, the box was first placed and cured at110° C. oven for 10 minutes, followed by 24 hours curing at roomtemperature. The top and bottom 0.5″ of the foam sample was removed, aswell as the paper lining sides of the foam. Samples were then cut andtested for flammability, including Federal Motor Vehicle Safety StandardNo. 302 (FMVSS 302), emission test per VDA 277.

Table 1 and 2 present the ingredients, parameters for the foampreparation and the results of the tests.

TABLE I Polyether flexible foam formulation system and test resultsFormulation (parts by weight) Foam 1 Foam 2 Foam 3 Polyol Voranol 8136100    100    100    Flame Retardant — Fyrol FR-2 New FR Product FRLoading —  8.00  4.00 Water  3.55  3.55  3.55 Niax A-1  0.06  0.06  0.06Dabco 33LV  0.19  0.19  0.19 Niax L-620  0.80  0.80  0.80 StannousOctoate  0.10  0.10  0.05 T-9 TDI Index <110>    <110>    <110>   Physical Properties Density (pcf)  1.80  1.96  1.95 Air Flow (scfm) 3.03.0 2.8 Flame/Emission Tests FMVSS 302 Fail SE SE (13 mm thickness) VDA277 Total Carbon Emission (μgC/g)  5.64  5.76  2.56 SE =Self-Extinguishing-Specimen, ignited but self-extinguished prior toentering the time zone

TABLE 2 Polyester flexible foam formulation system and test resultsFormulation (parts by weight) Foam 4 Foam 5 Foam 6 Desmophen 60WB01100    100    100    Flame Retardant — Fyrol A300-TB New FR Product FRLoading — 7   4   Water 4.0 4.0 4.0 Niax C-131NPF 1.1 1.1 1.1 Niax DMP0.2 0.2 0.2 Niax L-537XF 1.3 1.3 1.3 TDI Index (40% TDI80/60% <98>  <98>   <98>   TDI65) Physical Properties Density (pcf)  1.87  1.99  1.92Air Flow (scfm) 0.5 0.6 0.4 Flame/Emission Test FMVSS 302 Fail SE SE (13mm thickness) VDA 277 Total Carbon  4.23  5.50  3.21 Emission (μgC/g)

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiments disclosed as the best modecontemplated for carrying out this invention but that the invention willinclude all embodiments falling within the scope of the appended claims.

In the claims:
 1. -20. (Cancelled)
 21. A flame-retarded flexiblepolyurethane foam comprising a flame retardant-effective amount of thereaction product of a polyol, an isocyanate and a phosphorus-containingpolyol reaction product of the partial phosphorylation of a polyalcohol,wherein the phosphorus-containing polyol reaction product is of theformula (I-B):

wherein: R¹ and R² are independently selected from a linear or branchedalkyl group containing from 1 to 4 carbon atoms, n¹ is an integer equalto or greater than 1 and n² is one, with n¹+n² being equal to or greaterthan 2, and Z² is a moiety derived from a branched polyol which has avalence of n¹+n², and is of the general formula:

wherein R is selected from the group consisting of:

and where each R⁶ independently is 1-I or is an alkyl of from 1 to 4carbon atoms, x≥0, y is 2 or 3; z is an integer of from 2 to 5; and,m≥1.
 22. The flame-retarded flexible polyurethane foam of claim 21,wherein R¹ and R² are each an ethyl group.
 23. An article comprising thepolyurethane foam of claim
 21. 24. The article of claim 23 wherein thearticle is suitable for use in an application selected from the groupconsisting of furniture applications, automotive applications, boatingapplications, bus seating applications, train seating applications, RVseating applications, office furniture seating applications, aviationapplications, tractor applications, bicycle applications, engine mountapplications, compressor applications, bedding applications, insulationapplications, sporting goods applications, shoe applications, carpetcushioning applications, packaging applications, textile applications,buffer cushioning applications, HVAC applications, tent applications,life raft applications, luggage applications, and hand bag applications.25. The article of claim 24, wherein said furniture applications areselected from upholstered furniture applications.
 26. The article ofclaim 24, wherein said automotive applications are selected from thegroup consisting of automotive seat cushions, head linings and headrests, back cushions for automobiles and trucks, bus seating, vehicleseat bottom and back bolsters, armrests, and support rings for run flattires.
 27. The article of claim 24 wherein the bedding applications areselected from the group consisting of mattresses and mattress topapplications.
 28. The article of claim 24 wherein said insulationapplications are sound insulation applications.